In addition to the placement of the Preedit/Status window for the root
window style, you can configure the behavior of the preedit string when it
reaches to the end of a line. In the default, the preedit string will wrap
around to the second line. But if you de-select "Wrap long lines in
on-the-spot preedit," the preedit string will not exceed one line and
it will scroll when reaching the end of a line.